pthread_create C++ and variable problems

Im trying to create a multithreaded C++ server.  The code compiles
cleanly and runs, but then I SEGV because apparently my private member
variables arent what they were when I 'new'd the class.

Here's my code:

main server loop:
---------------------

SERV_ARGS *largs;  // struct to pass
while(loop)
{
  int this_fd = accept(m_fd,(SOCKADDR *)&m_sa,&m_sa_len);
  if (this_fd > 0)
  {
     ServFD *sfd = new ServFD(this_fd);
     sfd->Start(largs);
     usleep(200);
   }
}

in ServFD:  // some code excluded for brevity
-------------------------------------------------------

extern "C" {
void *start_thread(void *args)
{
    ServFD *serv = (ServFD *)args;
    serv->ServFDThreadFunc();
    return 0;
}
};

ServFD::ServFD(int fd) :
    m_fd(fd),
    m_run(false)
{
}

int
ServFD::Start(SERV_ARGS *args)
{
    int ret = pthread_create(&thread_id, NULL, start_thread, (void
*)args);
    if (ret != 0)
    {
        logit(TERR, "ERROR pthread_create failed : %s <%d>",
            strerror(errno), errno);
        return -1;
    }
    //m_run = true;   <---- Gets a SEGV
    return 0;
}

void
ServFD::ServFDThreadFunc()
{
    while (m_run)
    {
        handle client here etc
    }
}

My problem seems to be that my private member variable m_fd is
no longer what I sent in on my 'new'.  It was 4, but by the time it
gets
to 'ServFDThreadFunc() its a huge number (bashed - 10732512).

Also when I set m_run = true above, it will SEGV.  Its like the values
were never instantiated.  So to get beyond that I stubbed out the
m_run
stuff but the same was true for m_fd and Im assuming anything else
I would otherwise use.

Can someone tell me why this is happening and how to fix it?

My assumption is that something is happening after the call to
pthread_create and somehow my ServFD class is no longer the
same ServFD class I 'new'd the first time, but Im unsure.

Any help is appreciated.
Thanks